How can we say nobody's perfect if there is no perfect to compare to? Perfection implies that there really is a right and wrong way to be. And what type of perfection is the best type? Moral perfection? Aesthetic? Physiological? Mental?
Money was established for exchange, but interest causes it to be reproduced by itself. Therefore this way of earning money is greatly in conflict with the natural law.
If you first fortify yourself with the true knowledge of the Universal Self, and then live in the midst of wealth and worldliness, surely they will in no way affect you.